Rattlesnake Hills is a small sub-region of Yakima Valley in Washington's Columbia Valley. The AVA encompasses 68,500 acres (27,720ha) along the northern edge of the Yakima Valley AVA, on slopes and terraces with a variety of aspects and inclines. The city of Yakima is just a few miles north-west of the AVA's boundary, and the smaller AVA of Snipes Mountain can be found just south of the Rattlesnake Hills. A wide variety of grapes are grown here, the most important of which are Merlot, Cabernet Sauvignon, Riesling and Malbec.
Commercial viticulture arrived in Rattlesnake Hills in 1968, when the area's first vineyard was planted to Riesling and Cabernet Sauvignon. The industry here grew steadily over the next 30 years, and when the area became an AVA in 2006, around 1500 acres (600ha) were in vine. The establishment of Rattlesnake Hills as an AVA was controversial. Opponents argued that the terroir was not distinctive enough and that granting the designation would undermine the power of the larger Yakima Valley AVA. But the Alcohol and Tobacco Tax and Trade Bureau concluded that there were enough differences and the AVA was granted.
Elevation has been cited as the main point of difference for the Rattlesnake Hills AVA. Vines are planted at least 850ft (260m) above sea level, on ridges and terraces where excellent air flow reduces the risk of disease and frost damage. The elevation also contributes to the diurnal temperature variation throughout the growing season, contributing to the balance of ripeness and acidity in the grapes. Below the vineyards, on the Yakima Valley floor, conditions are not as well suited to viticulture due to the poor air flow and the high water table.
Temperatures in the AVA are moderate during the growing season, with the Cascade Mountains to the west shielding the region from the influence of the Pacific Ocean. The Rattlesnake Hills also protect vineyards from polar blasts originating in Canada. These influences make the AVA considerably warmer (up to 10F/6C) in winter than its neighbors – another factor in reducing vine-killing frosts.
The soils in Rattlesnake Hills are predominantly silt loam, finer than the sandy compositions found elsewhere in the Columbia Valley. These soils are remnants from the extensive Missoula floods of the last Ice Age that shaped much of the landscape in the Columbia Basin before flowing south toward the Willamette Valley in Oregon. There is also some volcanic influence in the loam soils, left over from the eruption of Mount St. Helens in Washington in 1980. Consistent pH levels are credited with creating balanced flavors in the grapes.